Author: Robert Hyatt
Date: 20:05:39 12/13/02
Go up one level in this thread
On December 13, 2002 at 21:16:55, Matt Taylor wrote: >On December 12, 2002 at 10:15:16, Vincent Diepeveen wrote: > >>On December 11, 2002 at 02:34:33, Matt Taylor wrote: >> >>[snip] >>>Eugene's explanation fits, though. I am suprised that Intel did not duplicate >>>the trace cache for both logical CPUs. It's like trying to fit an even bigger >>>peg into an already too small hole... >>>-Matt >> >>Exactly, but the hardware reason to do that is very simply. >> >>They can clock the thing to 3.04Ghz now. 2.8Ghz for the Xeon. >> >>But if you double the L1 data cache size or the trace cache size >>(i will not do a statement what in my eyes is smarter to duplicate >>because you can see my next sentence why) then you have a major other >>problem. >> >>You won't be able to clock it to 3.04Ghz then nor 2.8Ghz for the Xeon. >> >>If you have something small, you can clock it high. >> >>If you have something big like an Itanium2 or the 128KB L1 cache >>of a K7 then you can't clock it that easily to 3.04Ghz. >> >>So the clocking and the size of such important integrated things into >>the procesor is very closely related. > >Actually that's not true. There are some 42 million transistors on the P4 >Northwood -- more than on Athlon or any IA-32 processor prior to it. Yet it >clocks up higher than any competing chips have. The trick isn't to make things >simple; it's to split them up. > >Two independant trace caches would scale fine without adding significant cost to >the processor. However, it would impede Intel profit margins because it would >require a bit of redesign. > >-Matt I don't think anyone would want two separate trace caches, as that would violate the very principle of hyper-threading. Rather, a larger trace cache, with a wider path out so that 2x the micro-ops can be spit out at once would be the hyper-thread design approach keeping with the spirit of SMT overall.
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.